The human papillomaviruses (HPVs) are infectious viruses that cause benign papillomas (warts) of the skin and mucous membranes. Of particular relevance to the field of human cancer, a subset of HPVs including HPV 16, is capable of inducing malignant progression from papilloma to cancer. The HPV 16 E6 oncoprotein interacts with and targets the degradation of the important tumor suppressor gene product p53, which is believed as a guardian of cells. However, the association with p53 does not explain all the functions of E6. The recent identification of E6BP, a novel E6-binding protein, has provided novel insights into the mechanism of transformation mediated by E6. The goal of this fellowship is to characterize E6BP and its interaction with HPV 16 E6. In the first objective, HPV 16 E6 mutants which are E6BP-binding defective but p53-degradation competent will be screened. This will be accomplished utilizing the two-hybrid screen in yeast and in vitro protein binding and degradation assays. Next the biological properties of these E6 mutants will be tested to determine how important the interaction with E6BP is to E6 functions. In the second objective, the yeast two-hybrid system will be utilized to screen for human cDNAs encoding E6BP-interacting proteins. These proteins will be characterized for their interactions with E6BP, including physical association and localization. These studies should provide insights into the mechanism by which the important viral protein E6 functions.